Field of the Invention
The present invention relates to an optical network arrangement for connecting a plurality of users, even in relatively high number, with a reduced number of optical fibers, and particularly to the deployment of cables for the connection of users to optical networks.
Overview of the Related Art
The deployment of broadband telecommunications networks calls for using optical fibers for the so-called “last mile”, i.e. the last trunk of the telecommunications network to which network termination devices, like for instance modems, network termination units (NTU) or, set-top boxes for receiving cable television services are directly connected. User devices such as computers, IP (Internet Protocol) phones and similar devices connect to the broadband telecommunications network via the network termination device.
Typically, the deployment of the last mile of an optical telecommunication network provides for the lay in the field of optical cables containing a plurality of optical fibers, for instance in a number variable from 6 to 48. The cables are routed through conduits that can for example develop through or along the walls of a multi-floor building, often for more or less vertical segments, or, in the case of separate buildings set in succession along a city street, the optical cables extend horizontally through conduits preferably located under of the ground level.
Typically, an optical cable of the type adapted for this use includes a tubular element, or sheath, inside which several optical fibers are placed. Depending on the specific type of application, the optical fibers can be accommodated within the sheath without protections, or they may be covered by a protective coating, or they may also be gathered in independent groups (also referred to as microcables or micromodules) contained in a thin tubular coating.
In order to make the connection of the different users to the optical network, it is necessary to lead one or more optical fibers to the sites (apartments, houses, offices) of the users. To this end, openings need to be made in the sheath of the optical cables, so as to be able to access the optical fibers accommodated within each cable. Through such openings, the optical fibers can be at least partially drawn out, extracted from the cable and routed where needed, for example to sockets provided for in the premises of the users, to which the respective users can be connected.
An example of such deployment is provided by WO 2009/113112 in the name of the same present Applicant, wherein optical fiber units contained in an optical cable are connected to users by means of the phases of: providing an opening in a sheath of the optical cable to access the optical fiber units contained in the optical cable; extracting a segment of at least one optical fiber unit from the optical cable through the opening; inserting a free end of the extracted segment of optical fiber unit into a protection tube; making the protection tube slide on the extracted segment of optical fiber unit to insert an end portion of the protection tube, distal from the free end of the extract segment of the optical fiber unit, into the optical cable through the opening; positioning a closure element on the optical cable in correspondence of the opening so as to substantially realize a closure thereof; securing in removable way the closure element to the optical cable and bringing the free end of the extracted segment of optical fiber unit in correspondence of a connection point of a user device.
Another type of deployment for connecting different users is disclosed, for example, in WO 2006/13655, wherein an optical cable is disclosed containing several optical microcables where two openings in the external sheath are made: a first opening in correspondence of the point at which the cabling for the connection of a subscriber has to be realized, and a second opening downstream thereof, at a distance of the order of about some meters or tens of meters from the first opening. One of the optical microcables contained in the optical cable is selected (for example based on its color) and cut in correspondence of the second opening, and the segment of microcable between the first opening and the point of cut is then extracted from the optical cable through the first opening. The extracted microcable segment is then inserted into a pre-installed microconduit that extends to the connection point of the subscriber, or, depending on the circumstance, to a branch box.
Finally, US 2008/0240662 discloses a duplicated use of optical fibers in an optical cable. The optical cable comprises a main optical fiber module and a secondary optical fiber module. Optical fibers of the main optical fiber module are sectioned, at one end, and connected to optical fibers of the secondary optical fiber module in order to form a connection loop.